File: expire.c

package info (click to toggle)
linux 4.19.37-3
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 962,264 kB
  • sloc: ansic: 16,757,120; asm: 271,404; makefile: 38,285; sh: 33,529; perl: 27,681; python: 21,031; cpp: 5,063; yacc: 4,648; lex: 2,585; awk: 1,385; ruby: 25; sed: 5
file content (661 lines) | stat: -rw-r--r-- 15,633 bytes parent folder | download | duplicates (5)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
/*
 * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 * Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
 * Copyright 2001-2006 Ian Kent <raven@themaw.net>
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 */

#include "autofs_i.h"

/* Check if a dentry can be expired */
static inline int autofs_can_expire(struct dentry *dentry,
				    unsigned long timeout, unsigned int how)
{
	struct autofs_info *ino = autofs_dentry_ino(dentry);

	/* dentry in the process of being deleted */
	if (ino == NULL)
		return 0;

	if (!(how & AUTOFS_EXP_IMMEDIATE)) {
		/* Too young to die */
		if (!timeout || time_after(ino->last_used + timeout, jiffies))
			return 0;
	}
	return 1;
}

/* Check a mount point for busyness */
static int autofs_mount_busy(struct vfsmount *mnt,
			     struct dentry *dentry, unsigned int how)
{
	struct dentry *top = dentry;
	struct path path = {.mnt = mnt, .dentry = dentry};
	int status = 1;

	pr_debug("dentry %p %pd\n", dentry, dentry);

	path_get(&path);

	if (!follow_down_one(&path))
		goto done;

	if (is_autofs_dentry(path.dentry)) {
		struct autofs_sb_info *sbi = autofs_sbi(path.dentry->d_sb);

		/* This is an autofs submount, we can't expire it */
		if (autofs_type_indirect(sbi->type))
			goto done;
	}

	/* Not a submount, has a forced expire been requested */
	if (how & AUTOFS_EXP_FORCED) {
		status = 0;
		goto done;
	}

	/* Update the expiry counter if fs is busy */
	if (!may_umount_tree(path.mnt)) {
		struct autofs_info *ino;

		ino = autofs_dentry_ino(top);
		ino->last_used = jiffies;
		goto done;
	}

	status = 0;
done:
	pr_debug("returning = %d\n", status);
	path_put(&path);
	return status;
}

/*
 * Calculate and dget next entry in the subdirs list under root.
 */
static struct dentry *get_next_positive_subdir(struct dentry *prev,
					       struct dentry *root)
{
	struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
	struct list_head *next;
	struct dentry *q;

	spin_lock(&sbi->lookup_lock);
	spin_lock(&root->d_lock);

	if (prev)
		next = prev->d_child.next;
	else {
		prev = dget_dlock(root);
		next = prev->d_subdirs.next;
	}

cont:
	if (next == &root->d_subdirs) {
		spin_unlock(&root->d_lock);
		spin_unlock(&sbi->lookup_lock);
		dput(prev);
		return NULL;
	}

	q = list_entry(next, struct dentry, d_child);

	spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
	/* Already gone or negative dentry (under construction) - try next */
	if (!d_count(q) || !simple_positive(q)) {
		spin_unlock(&q->d_lock);
		next = q->d_child.next;
		goto cont;
	}
	dget_dlock(q);
	spin_unlock(&q->d_lock);
	spin_unlock(&root->d_lock);
	spin_unlock(&sbi->lookup_lock);

	dput(prev);

	return q;
}

/*
 * Calculate and dget next entry in top down tree traversal.
 */
static struct dentry *get_next_positive_dentry(struct dentry *prev,
					       struct dentry *root)
{
	struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
	struct list_head *next;
	struct dentry *p, *ret;

	if (prev == NULL)
		return dget(root);

	spin_lock(&sbi->lookup_lock);
relock:
	p = prev;
	spin_lock(&p->d_lock);
again:
	next = p->d_subdirs.next;
	if (next == &p->d_subdirs) {
		while (1) {
			struct dentry *parent;

			if (p == root) {
				spin_unlock(&p->d_lock);
				spin_unlock(&sbi->lookup_lock);
				dput(prev);
				return NULL;
			}

			parent = p->d_parent;
			if (!spin_trylock(&parent->d_lock)) {
				spin_unlock(&p->d_lock);
				cpu_relax();
				goto relock;
			}
			spin_unlock(&p->d_lock);
			next = p->d_child.next;
			p = parent;
			if (next != &parent->d_subdirs)
				break;
		}
	}
	ret = list_entry(next, struct dentry, d_child);

	spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
	/* Negative dentry - try next */
	if (!simple_positive(ret)) {
		spin_unlock(&p->d_lock);
		lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
		p = ret;
		goto again;
	}
	dget_dlock(ret);
	spin_unlock(&ret->d_lock);
	spin_unlock(&p->d_lock);
	spin_unlock(&sbi->lookup_lock);

	dput(prev);

	return ret;
}

/*
 * Check a direct mount point for busyness.
 * Direct mounts have similar expiry semantics to tree mounts.
 * The tree is not busy iff no mountpoints are busy and there are no
 * autofs submounts.
 */
static int autofs_direct_busy(struct vfsmount *mnt,
			      struct dentry *top,
			      unsigned long timeout,
			      unsigned int how)
{
	pr_debug("top %p %pd\n", top, top);

	/* Forced expire, user space handles busy mounts */
	if (how & AUTOFS_EXP_FORCED)
		return 0;

	/* If it's busy update the expiry counters */
	if (!may_umount_tree(mnt)) {
		struct autofs_info *ino;

		ino = autofs_dentry_ino(top);
		if (ino)
			ino->last_used = jiffies;
		return 1;
	}

	/* Timeout of a direct mount is determined by its top dentry */
	if (!autofs_can_expire(top, timeout, how))
		return 1;

	return 0;
}

/*
 * Check a directory tree of mount points for busyness
 * The tree is not busy iff no mountpoints are busy
 */
static int autofs_tree_busy(struct vfsmount *mnt,
			    struct dentry *top,
			    unsigned long timeout,
			    unsigned int how)
{
	struct autofs_info *top_ino = autofs_dentry_ino(top);
	struct dentry *p;

	pr_debug("top %p %pd\n", top, top);

	/* Negative dentry - give up */
	if (!simple_positive(top))
		return 1;

	p = NULL;
	while ((p = get_next_positive_dentry(p, top))) {
		pr_debug("dentry %p %pd\n", p, p);

		/*
		 * Is someone visiting anywhere in the subtree ?
		 * If there's no mount we need to check the usage
		 * count for the autofs dentry.
		 * If the fs is busy update the expiry counter.
		 */
		if (d_mountpoint(p)) {
			if (autofs_mount_busy(mnt, p, how)) {
				top_ino->last_used = jiffies;
				dput(p);
				return 1;
			}
		} else {
			struct autofs_info *ino = autofs_dentry_ino(p);
			unsigned int ino_count = atomic_read(&ino->count);

			/* allow for dget above and top is already dgot */
			if (p == top)
				ino_count += 2;
			else
				ino_count++;

			if (d_count(p) > ino_count) {
				top_ino->last_used = jiffies;
				dput(p);
				return 1;
			}
		}
	}

	/* Forced expire, user space handles busy mounts */
	if (how & AUTOFS_EXP_FORCED)
		return 0;

	/* Timeout of a tree mount is ultimately determined by its top dentry */
	if (!autofs_can_expire(top, timeout, how))
		return 1;

	return 0;
}

static struct dentry *autofs_check_leaves(struct vfsmount *mnt,
					  struct dentry *parent,
					  unsigned long timeout,
					  unsigned int how)
{
	struct dentry *p;

	pr_debug("parent %p %pd\n", parent, parent);

	p = NULL;
	while ((p = get_next_positive_dentry(p, parent))) {
		pr_debug("dentry %p %pd\n", p, p);

		if (d_mountpoint(p)) {
			/* Can we umount this guy */
			if (autofs_mount_busy(mnt, p, how))
				continue;

			/* This isn't a submount so if a forced expire
			 * has been requested, user space handles busy
			 * mounts */
			if (how & AUTOFS_EXP_FORCED)
				return p;

			/* Can we expire this guy */
			if (autofs_can_expire(p, timeout, how))
				return p;
		}
	}
	return NULL;
}

/* Check if we can expire a direct mount (possibly a tree) */
static struct dentry *autofs_expire_direct(struct super_block *sb,
					   struct vfsmount *mnt,
					   struct autofs_sb_info *sbi,
					   unsigned int how)
{
	struct dentry *root = dget(sb->s_root);
	struct autofs_info *ino;
	unsigned long timeout;

	if (!root)
		return NULL;

	timeout = sbi->exp_timeout;

	if (!autofs_direct_busy(mnt, root, timeout, how)) {
		spin_lock(&sbi->fs_lock);
		ino = autofs_dentry_ino(root);
		/* No point expiring a pending mount */
		if (ino->flags & AUTOFS_INF_PENDING) {
			spin_unlock(&sbi->fs_lock);
			goto out;
		}
		ino->flags |= AUTOFS_INF_WANT_EXPIRE;
		spin_unlock(&sbi->fs_lock);
		synchronize_rcu();
		if (!autofs_direct_busy(mnt, root, timeout, how)) {
			spin_lock(&sbi->fs_lock);
			ino->flags |= AUTOFS_INF_EXPIRING;
			init_completion(&ino->expire_complete);
			spin_unlock(&sbi->fs_lock);
			return root;
		}
		spin_lock(&sbi->fs_lock);
		ino->flags &= ~AUTOFS_INF_WANT_EXPIRE;
		spin_unlock(&sbi->fs_lock);
	}
out:
	dput(root);

	return NULL;
}

/* Check if 'dentry' should expire, or return a nearby
 * dentry that is suitable.
 * If returned dentry is different from arg dentry,
 * then a dget() reference was taken, else not.
 */
static struct dentry *should_expire(struct dentry *dentry,
				    struct vfsmount *mnt,
				    unsigned long timeout,
				    unsigned int how)
{
	struct autofs_info *ino = autofs_dentry_ino(dentry);
	unsigned int ino_count;

	/* No point expiring a pending mount */
	if (ino->flags & AUTOFS_INF_PENDING)
		return NULL;

	/*
	 * Case 1: (i) indirect mount or top level pseudo direct mount
	 *	   (autofs-4.1).
	 *	   (ii) indirect mount with offset mount, check the "/"
	 *	   offset (autofs-5.0+).
	 */
	if (d_mountpoint(dentry)) {
		pr_debug("checking mountpoint %p %pd\n", dentry, dentry);

		/* Can we umount this guy */
		if (autofs_mount_busy(mnt, dentry, how))
			return NULL;

		/* This isn't a submount so if a forced expire
		 * has been requested, user space handles busy
		 * mounts */
		if (how & AUTOFS_EXP_FORCED)
			return dentry;

		/* Can we expire this guy */
		if (autofs_can_expire(dentry, timeout, how))
			return dentry;
		return NULL;
	}

	if (d_really_is_positive(dentry) && d_is_symlink(dentry)) {
		pr_debug("checking symlink %p %pd\n", dentry, dentry);

		/* Forced expire, user space handles busy mounts */
		if (how & AUTOFS_EXP_FORCED)
			return dentry;

		/*
		 * A symlink can't be "busy" in the usual sense so
		 * just check last used for expire timeout.
		 */
		if (autofs_can_expire(dentry, timeout, how))
			return dentry;
		return NULL;
	}

	if (simple_empty(dentry))
		return NULL;

	/* Case 2: tree mount, expire iff entire tree is not busy */
	if (!(how & AUTOFS_EXP_LEAVES)) {
		/* Not a forced expire? */
		if (!(how & AUTOFS_EXP_FORCED)) {
			/* ref-walk currently on this dentry? */
			ino_count = atomic_read(&ino->count) + 1;
			if (d_count(dentry) > ino_count)
				return NULL;
		}

		if (!autofs_tree_busy(mnt, dentry, timeout, how))
			return dentry;
	/*
	 * Case 3: pseudo direct mount, expire individual leaves
	 *	   (autofs-4.1).
	 */
	} else {
		struct dentry *expired;

		/* Not a forced expire? */
		if (!(how & AUTOFS_EXP_FORCED)) {
			/* ref-walk currently on this dentry? */
			ino_count = atomic_read(&ino->count) + 1;
			if (d_count(dentry) > ino_count)
				return NULL;
		}

		expired = autofs_check_leaves(mnt, dentry, timeout, how);
		if (expired) {
			if (expired == dentry)
				dput(dentry);
			return expired;
		}
	}
	return NULL;
}

/*
 * Find an eligible tree to time-out
 * A tree is eligible if :-
 *  - it is unused by any user process
 *  - it has been unused for exp_timeout time
 */
static struct dentry *autofs_expire_indirect(struct super_block *sb,
					     struct vfsmount *mnt,
					     struct autofs_sb_info *sbi,
					     unsigned int how)
{
	unsigned long timeout;
	struct dentry *root = sb->s_root;
	struct dentry *dentry;
	struct dentry *expired;
	struct dentry *found;
	struct autofs_info *ino;

	if (!root)
		return NULL;

	timeout = sbi->exp_timeout;

	dentry = NULL;
	while ((dentry = get_next_positive_subdir(dentry, root))) {
		spin_lock(&sbi->fs_lock);
		ino = autofs_dentry_ino(dentry);
		if (ino->flags & AUTOFS_INF_WANT_EXPIRE) {
			spin_unlock(&sbi->fs_lock);
			continue;
		}
		spin_unlock(&sbi->fs_lock);

		expired = should_expire(dentry, mnt, timeout, how);
		if (!expired)
			continue;

		spin_lock(&sbi->fs_lock);
		ino = autofs_dentry_ino(expired);
		ino->flags |= AUTOFS_INF_WANT_EXPIRE;
		spin_unlock(&sbi->fs_lock);
		synchronize_rcu();

		/* Make sure a reference is not taken on found if
		 * things have changed.
		 */
		how &= ~AUTOFS_EXP_LEAVES;
		found = should_expire(expired, mnt, timeout, how);
		if (!found || found != expired)
			/* Something has changed, continue */
			goto next;

		if (expired != dentry)
			dput(dentry);

		spin_lock(&sbi->fs_lock);
		goto found;
next:
		spin_lock(&sbi->fs_lock);
		ino->flags &= ~AUTOFS_INF_WANT_EXPIRE;
		spin_unlock(&sbi->fs_lock);
		if (expired != dentry)
			dput(expired);
	}
	return NULL;

found:
	pr_debug("returning %p %pd\n", expired, expired);
	ino->flags |= AUTOFS_INF_EXPIRING;
	init_completion(&ino->expire_complete);
	spin_unlock(&sbi->fs_lock);
	return expired;
}

int autofs_expire_wait(const struct path *path, int rcu_walk)
{
	struct dentry *dentry = path->dentry;
	struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
	struct autofs_info *ino = autofs_dentry_ino(dentry);
	int status;
	int state;

	/* Block on any pending expire */
	if (!(ino->flags & AUTOFS_INF_WANT_EXPIRE))
		return 0;
	if (rcu_walk)
		return -ECHILD;

retry:
	spin_lock(&sbi->fs_lock);
	state = ino->flags & (AUTOFS_INF_WANT_EXPIRE | AUTOFS_INF_EXPIRING);
	if (state == AUTOFS_INF_WANT_EXPIRE) {
		spin_unlock(&sbi->fs_lock);
		/*
		 * Possibly being selected for expire, wait until
		 * it's selected or not.
		 */
		schedule_timeout_uninterruptible(HZ/10);
		goto retry;
	}
	if (state & AUTOFS_INF_EXPIRING) {
		spin_unlock(&sbi->fs_lock);

		pr_debug("waiting for expire %p name=%pd\n", dentry, dentry);

		status = autofs_wait(sbi, path, NFY_NONE);
		wait_for_completion(&ino->expire_complete);

		pr_debug("expire done status=%d\n", status);

		if (d_unhashed(dentry))
			return -EAGAIN;

		return status;
	}
	spin_unlock(&sbi->fs_lock);

	return 0;
}

/* Perform an expiry operation */
int autofs_expire_run(struct super_block *sb,
		      struct vfsmount *mnt,
		      struct autofs_sb_info *sbi,
		      struct autofs_packet_expire __user *pkt_p)
{
	struct autofs_packet_expire pkt;
	struct autofs_info *ino;
	struct dentry *dentry;
	int ret = 0;

	memset(&pkt, 0, sizeof(pkt));

	pkt.hdr.proto_version = sbi->version;
	pkt.hdr.type = autofs_ptype_expire;

	dentry = autofs_expire_indirect(sb, mnt, sbi, 0);
	if (!dentry)
		return -EAGAIN;

	pkt.len = dentry->d_name.len;
	memcpy(pkt.name, dentry->d_name.name, pkt.len);
	pkt.name[pkt.len] = '\0';

	if (copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)))
		ret = -EFAULT;

	spin_lock(&sbi->fs_lock);
	ino = autofs_dentry_ino(dentry);
	/* avoid rapid-fire expire attempts if expiry fails */
	ino->last_used = jiffies;
	ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE);
	complete_all(&ino->expire_complete);
	spin_unlock(&sbi->fs_lock);

	dput(dentry);

	return ret;
}

int autofs_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
			   struct autofs_sb_info *sbi, unsigned int how)
{
	struct dentry *dentry;
	int ret = -EAGAIN;

	if (autofs_type_trigger(sbi->type))
		dentry = autofs_expire_direct(sb, mnt, sbi, how);
	else
		dentry = autofs_expire_indirect(sb, mnt, sbi, how);

	if (dentry) {
		struct autofs_info *ino = autofs_dentry_ino(dentry);
		const struct path path = { .mnt = mnt, .dentry = dentry };

		/* This is synchronous because it makes the daemon a
		 * little easier
		 */
		ret = autofs_wait(sbi, &path, NFY_EXPIRE);

		spin_lock(&sbi->fs_lock);
		/* avoid rapid-fire expire attempts if expiry fails */
		ino->last_used = jiffies;
		ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE);
		complete_all(&ino->expire_complete);
		spin_unlock(&sbi->fs_lock);
		dput(dentry);
	}

	return ret;
}

/*
 * Call repeatedly until it returns -EAGAIN, meaning there's nothing
 * more to be done.
 */
int autofs_expire_multi(struct super_block *sb, struct vfsmount *mnt,
			struct autofs_sb_info *sbi, int __user *arg)
{
	unsigned int how = 0;

	if (arg && get_user(how, arg))
		return -EFAULT;

	return autofs_do_expire_multi(sb, mnt, sbi, how);
}